Valve must be very pleased with how its sequel Portal 2 is performing.  The game has enchanted plenty of players since its release last April with over four million copies sold, according to the developer.  That’s a huge success and one that they continue to support today with new downloadable content.

The company has announced that its latest DLC, the Perpetual Testing Initiative, is now available for download on PC.  There still isn't an announcement for release on Xbox Live or PlayStation Network, but those who play the game on Steam should be enthralled to have access to such a bonus.

In it, you can create and play fan-made maps using the Hammer editor.  Even though it’s heavy on specs and takes a little getting used to, it's well-worth it as this is essentially the same in-house tool that Valve used for the original game.  

With the Perpetual Testing Initiative, you’re able to export your creations in this format and continue using the tools necessary to make the best level possible.  Valve considers it “incredibly powerful for all of its simplicity, and can easily reproduce pretty much every puzzle from Portal 2.”

We’ll give it a swing (you should too - it's free) and let you know how it is.